Sample injection valve for high-performacne liquid chromatography (hplc) devices

ABSTRACT

The sample injection valve for high-performance liquid chromatography (HPLC) devices comprises a stator with inlets for the sample and the mobile phase, outlets leading to the chromatography column and to a waste collector, as well as connections for both ends of a sample loop. Its rotor has the customary connection channels. An additional washing liquid inlet ( 7 ) opens into the connecting channel ( 9 ) that, in one valve position, connects the sample inlet ( 1 ) to the outlet ( 2 ) leading to the waste collector. This enables the sample inlet and the pipette or syringe located therein to be rinsed.

[0001] The invention relates to a sample injection valve for HPLCdevices which comprises a stator with inlets for the sample and themobile phase, outlets leading to the chromatography column and to awaste collector, as well as terminals for both ends of a sample loop,and a rotor with connection channels.

[0002] Sample injection valves of this type are in use in the majorityof known HPLC devices. The rotor has two possible positions. In oneposition the sample inlet is connected to one end of the sample loop sothat the latter is filled with sample. In the second position the sampleinlet is normally connected to the waste collector for disposal of theremaining sample that is not required. At the same time, in the secondposition the sample loop is switched between the inlet for the mobilephase and the outlet leading to the column. This second position of therotor thus corresponds to the sample injection phase, in which thequantity of sample measured into the loop is transported to the column.

[0003] The sample injection phase is utilized for cleaning the tip ofthe sample pipette in order to avoid contamination between successivesamples. For this purpose the pipette is conventionally transferred to aseparate cleaning device before being made available for collection ofthe next sample.

[0004] Although this method ensures that the tip is cleaned, no cleaningtakes place in the inlet region on the stator, which conventionally is atype of sleeve that tightly envelops the tip during injection of thesample. Increasing accuracy of measurement has revealed that there isindeed contamination in this region.

[0005] A further disadvantage of the known method is that the cleaningprocesses require more time than injection of the sample, so cleaningrepresents a limiting factor for the sample throughput per unit time.

[0006] The object of the invention is therefore to effect the cleaningof the pipette tip and sample inlet more reliably and more rapidly.

[0007] This object is achieved according to the invention by a sampleinjection valve of the type mentioned at the outset, in which provisionis made for an additional washing liquid inlet that, in one valveposition, in which the sample inlet is connected via a connectionchannel to the outlet leading to the waste collector, opens into saidconnection channel.

[0008] An embodiment of the invention is described below with the aid ofthe attached drawings, in which:

[0009]FIG. 1 is a schematic representation of a sample injection valvein one switching position, and

[0010]FIG. 2 shows the sample injection valve in its second position.

[0011] Both Figures schematically show the terminals and theirconnections. The external shape of the sample injection valve is notshown because it is irrelevant to its function and the possible shapesof such sample injection valves are sufficiently well known.

[0012] The sample injection valve shown in the Figures has the followingseven terminals on the stator: a sample inlet 1, a waste outlet 2, aterminal 3 for one end of a sample loop 8, a mobile phase inlet 4, acolumn terminal 5, a terminal 6 for the other end of the sample loop 8,and a washing liquid inlet 7 arranged between the sample inlet 1 and thewaste outlet 2. The terminals are interconnected in differentcombinations via connection channels in the rotor.

[0013] The connection channels in the rotor are formed by grooves in oneof the flat faces of the rotor. In the present embodiment the rotor hasthree grooves 9, 10 and 11. The rotor is switched between two positionsto create the following connections:

[0014] In the position shown in FIG. 1 the sample inlet is connected viathe groove 9 to one end of the sample loop, the other end beingconnected via the groove 10 to the waste outlet 2. The groove 11connects the mobile phase inlet 4 to the column terminal. In thisposition the sample loop is filled with sample by means of a pipette tipor syringe needle inserted in the sample inlet, any excess running intothe waste. At the same time the column is rinsed with mobile phase. Thewashing liquid inlet 7 is closed.

[0015] In the position shown in FIG. 2 the sample inlet 1 is connectedvia the groove 9 to the washing liquid inlet 7 and the waste outlet 2.At the same time the groove 10 connects one end 3 of the sample loop 8to the mobile phase inlet 4 and the groove 11 connects the other end 6of the sample loop 8 to the column terminal 5. The latter connectionallows the quantity of sample present in the sample loop 8 to be fedinto the column.

[0016] The connection of the sample inlet 1 to the washing liquid inlet7 in the second position of the rotor, shown in FIG. 2, allows thepipette or syringe to suck up the quantity of washing liquid requiredfor cleaning and then to discharge it into the waste. A check valve 12is arranged in the line leading to the waste collector, directly outsidethe waste outlet, in order to prevent liquid flowing back from the wasteinto the pipette while it is being sucked up.

[0017] A feed line 13, in which a stop valve 14 is arranged, leads tothe washing liquid inlet 7. Said stop valve 14 is operated for cleaningof the sample injection valve and injection syringe and is open forsucking up the washing liquid and closed for discharging it.

[0018] After this cleaning step the pipette or syringe is immediatelyready for collection of the next sample. The time previously needed totransfer the pipette to the cleaning device is eliminated, therebymarkedly increasing the sample throughput rate.

1. Sample injection valve for HPLC devices which comprises a stator withinlets for the sample and the mobile phase, outlets leading to thechromatography column and to a waste collector, as well as terminals forboth ends of a sample loop, and a rotor with connection channels,characterized in that provision is made for an additional washing liquidinlet (7) that, in one valve position, in which the sample inlet (1) isconnected via a connection channel (9) to the outlet (2) leading to thewaste collector, opens into said connection channel.
 2. Sample injectionvalve according to claim 1, characterized by a check valve (12) at theoutlet (2) leading to the waste collector.